1. Field of the Invention
The present invention relates to a pixel structure and a fabricating method thereof, and particularly to a pixel structure for use in a liquid crystal display (LCD) device and a method of fabricating the same.
2. Description of Related Art
Thin film transistor liquid crystal displays are generally classified into three types, namely, the transmissive type, the reflective type and the transflective type. This classification is based on the light sources utilized and the differences in the array substrate. The transmissive type thin film transistor liquid crystal display (transmissive TFT-LCD) device mainly utilizes a back-light as the light source. The pixel electrodes on the thin film transistor array substrate are transparent electrodes to facilitate the penetration of light from the back-light source. The reflective thin film transistor liquid crystal display (reflective TFT-LCD) device mainly utilizes a front-light or an external light as its light source. The pixel electrodes on the thin film transistor array substrate are reflective metal electrodes or other reflective electrodes with good reflection properties suitable for reflecting light from the front-light source or the external light source. On the other hand, the transflective thin film transistor liquid crystal display (transflective TFT-LCD) device can be regarded as a structure that integrates both the transmissive TFT-LCD device and the reflective TFT-LCD device. The transflective TFT-LCD device can utilize both a back-light source and a front-light source or an external light source simultaneously to display images.
FIGS. 1A to 1D are cross-sectional views showing the conventional fabrication flowchart of a pixel structure used in the transflective LCD device. Referring to FIG. 1A, the conventional fabricating process of the pixel structure includes the following steps. First, a substrate 110 is provided, whereon a gate 120, a gate insulation layer 130, a semiconductor layer 140, a source 150a and a drain 150b are formed in order. The gate 120 is covered by the gate insulation layer 130. The semiconductor layer 140 is disposed on the gate insulation layer 130 above the gate 120. The source 150a and the drain 150b are disposed on the semiconductor layer 140.
Referring to FIG. 1B, a protective layer 160, formed on the gate insulation layer 130, has a contact hole 160a to expose a portion of the drain 150b. Next, a plurality of bumps 170 is formed on the protective layer 160. More specifically, a patterned photo-resistant layer (not shown) is formed on the protective layer 160, and then a reflowing process is performed to form the bumps 170.
Referring to FIGS. 1C and 1D, a reflective pixel electrode 180a and a transparent pixel electrode 180b are formed in order over the protective layer 160. The reflective pixel electrode 180a covers the bumps 170 and is electrically connected with the drain 150b through the contact hole 160a. Moreover, the transparent pixel electrode 180b covers the reflective pixel electrode 180a and is electrically connected with the drain 150b through the reflective pixel electrode 180a. 
Since the reflective pixel electrode 180a covers the bumps 170, the light reflection rate can be increased. However, because the bumps 170 are made of a photo-resistant material and the photo-resistant material contains solvents, the bumps 170 may result in low reliability. Besides, the bumps 170 also introduce an additional cost.